4.1. REGULATED PARAMETERS OF RCD

According to GOST R 50807-95, the following RCD parameters are standardized:

• Rated voltage (U n ) - RMS voltage value at which the RCD operability is ensured. U n \u003d 220, 380 V.
• Rated load current (I n ) - the value of the current that the RCD can pass in continuous operation. I n \u003d 6; 16; 25; 40; 63; 80; one hundred; 125 A.
• Rated residual breaking current (I D n ) - the value of the differential current that causes the RCD to trip under the specified operating conditions. I D n \u003d 0.006; 0.01; 0.03; 0.1; 0.3; 0.5 A.
• Rated non-breaking differential current (I D n0 ) - the value of the differential current, which does not cause the RCD to trip under the specified operating conditions. I D n0 \u003d 0.5 I D n.
• Non-breaking overcurrent limit (I nm ) - the minimum value of non-disconnecting overcurrent at symmetrical load of two and four-pole RCDs or unbalanced load of four-pole RCDs. I nm \u003d 6 I n.
• Overcurrent - any current that exceeds the rated load current.
• Rated making and breaking capacity (switching capacity) (I m ) - the effective value of the expected current that the RCD is able to turn on, pass during its opening time and turn off under specified operating conditions without disrupting its performance. Minimum value I m \u003d 10 I n or 500 A whichever is greater.
• Rated making and breaking capacity for residual current (I D m ) - the effective value of the expected differential current, which the RCD is able to turn on, pass during its opening time and turn off under specified operating conditions without disrupting its performance. Minimum value of I D m \u003d 10 I n or 500 A, whichever is greater.
• Rated conditional short-circuit current (I nc ) - the effective value of the prospective current that is capable of withstanding the RCD protected by the short-circuit protection device, under the specified operating conditions, without irreversible changes that disrupt its performance. I nc \u003d 3000; 4500; 6000; 10,000 A.
• Rated conditional residual short-circuit current (I D c ) - the effective value of the expected differential current that is able to withstand the RCD protected by the short-circuit protection device under the specified operating conditions without irreversible changes that impair its performance. I D c \u003d 3000; 4500; 6000; 10,000 A.

GOST R 51326.1-99 contains the requirement: "The manufacturer must report the values \u200b\u200bof the Joule integral (I 2 t) and the peak current (I p) withstand by the RCD. If they are not defined, the minimum values \u200b\u200bare used (Table 4.1)."

Table 4.1.

I nc and I D c	I p, kA I 2 t, kA 2 * c	I n? 16	16 < I n ? 32	32 < I n ? 40	40 < I n ? 63	63 < I n ? 80	80 < I n ? 125
3000	I p	1.10	1.85	2.35	3.30	3.70	3.95
	I 2 t	1.20	4.50	8.70	22.5	36.0	65.0
4500	I p	1.15	2.05	2.70	3.90	4.80	5.60
	I 2 t	1.45	5.00	9.70	25.0	40.0	72.5
6000	I p	1.30	2.30	3.00	4.05	5.10	5.80
	I 2 t	1.60	6.00	11.5	28.0	47.0	82.0

Rated breaking time T n - the time interval between the moment of sudden occurrence of the tripping differential current and the moment of extinguishing the arc at all poles.

The standard values \u200b\u200bof the maximum permissible trip time of AC type RCDs at any rated load current and the values \u200b\u200bof the differential current specified by the standards should not exceed those given in table. 4.2.

Table 4.2.

The maximum shutdown time set in table. 4.2, also applies to RCDs of type A. In this case, tests of RCDs of type A are carried out at the values \u200b\u200bof currents ID n, 2I D n, 5I D n and 500 A with a coefficient of 1.4 (with ID n\u003e 0.01 A) and with a coefficient 2 (for ID n \u003d

The standard values \u200b\u200bof the permissible tripping and non-tripping times for type S RCDs at any rated load current over 25 A and values \u200b\u200bof the rated residual current over 0.03 A should not exceed those given in table. 4.3.

Table 4.3.

In fig. 4.1 shows a graphical interpretation of the RCD trip area depending on the multiplicity of the differential current.

Fig 4.1. Time-current characteristic of RCD

As an example of the execution of an RCD that meets all the requirements of GOST R 50807-95, in table. 4.4 shows the technical characteristics of ASTRO * UZO produced by OPZ MEI. In fig. 4.2 shows the appearance of the RCD.

Table 4.4.

Parameter name	Nominal value
Rated voltage U n, V	220, 380*
Frequency f n, Hz	50
Rated load current I n, A	16, 25, 40, 63, 80*
Rated breaking differential current (setting) I D n, mA	10, 30, 100, 300*
Rated non-breaking residual current I D n0	0.5 I D n
Rated making and breaking (switching) capacity I m, A	1500
Rated conditional short-circuit current (thermal withstand) with a fuse-link connected in series 63 A I nc, A	10000
Rated breaking time at rated differential current T n, no more, ms	30
Range of working temperatures, о С	-25 - 40
Maximum cross-section of connected wires, mm 2	25.50*
Service life: electrical cycles, not less	4000
mechanical cycles, not less	10000

* Depending on the device modification

Examples of characteristics (parameters) of various types of RCDs:

Design features of the residual current device type VD1-63 type A and AC (IEK):

Differential switch VD 1-63 type A (IEK companies):

Unlike the majority of similar product samples presented by Russian companies on the market, VD 1-63 type A simultaneously has all the advantages of an electromechanical RCD (operates in all cases, even if the neutral conductor is broken) and RCD type A (provides a more complete than RCD type AC, protection of a person from electric shock).

VD 1-63 belongs to the class of RCDs of type A and is capable of responding not only to sinusoidal alternating differential current, but also to pulsating direct current. VD 1-63 fully complies with the requirements of GOST 50326 and GOST 50807 as a differential switch “functionally independent of the power source”.

Among the largest Russian electrical engineering companies, IEK Group of Companies became the first company to produce an apparatus of this level of protection (see Fig. 1):

Figure: 1 Three-phase and single-phase electromechanical RCD type A

Until now, type A RCDs have been supplied to the market mainly by foreign companies. Introducing VD 1-63 to the market, IEK Group of Companies provides the consumer with a reliable anti-jamming electromechanical RCD capable of providing more complete protection than an AC type RCD against electric shock in case of accidental unintentional contact with a conductor and protection against leakage currents.

VD 1-63 is designed for use in power grids to which modern household appliances (TVs, washing machines, computer equipment, etc.) can be connected, as well as for power supply of industrial facilities that use electronic equipment.

The operation of type A RCDs is recommended by the PUE (7th edition) and the Temporary Instructions for the Use of RCDs in electrical installations of residential buildings. “In residential buildings, as a rule, type A RCDs should be used, which react not only to alternating, but also to pulsating fault currents. The use of AC type RCDs that react only to alternating leakage currents is allowed in justified cases. "

The main advantages of VD 1-63 type A are:

• Uniqueness:
  most of the largest Russian manufacturers of electrical equipment have no analogues of this equipment.
• Reliability:
  an electromechanical RCD is capable of operating without auxiliary power sources, while it has a characteristic A of operation by differential current.
• High mechanical durability:
  not less than 10,000 inclusions.
• Silver soldered contacts.
• Wide range in accordance with the requirements of the standard:
  from 10 to 100 mA.
• Price:
  2 times lower than that of foreign manufacturers (at least, than that of ABB, author's note).

Design features

• Electromechanical circuit without electronic components.
• Remains operational in the event of a break in the neutral conductor.
• Does not require auxiliary power supplies.
• Remains operational at any voltage.
• Wide operating voltage range of the in-service monitor (115 to 265 V in 2-pin and 200 to 400 V in 4-pin).
• Wide operating temperature range: from -25 to + 40 ° С.
• Increased response time due to the use of a special design of the release mechanism.
• Connection invariance (network connection from either side), ease of installation.
• Connection of conductors up to 50 mm 2.
• Contact position indicator.

Specifications:

Compliant with standards	GOST R 51326.1, GOST R 51326.2.1, TU 3422-033-18461115-2010
Rated current In, A	16, 25, 32, 40, 50, 63
Rated breaking residual current IDn, mA
Rated conditional differential short-circuit current IDc, A
Operating characteristic in case of differential current with DC component, type
Tripping time at rated differential current, ms	no more than 40
Number of poles
terms of Use
Breaker protection degree
Electrical durability, cycles V-O, not less
Mechanical durability, cycles B-O, not less
Maximum cross-section of the connected wires, mm2
Weight (2/4-pole), kg

Differential switch VD 1-63 AC type (IEK companies):

• Residual current device VD1-63 AC type is a reliable anti-jamming electromechanical RCD capable of providing protection against electric shock in case of accidental unintentional contact with the conductor and protection against leakage currents.
• Differential switch VD1-63 type AC belongs to the class of RCD type AC and reacts to differential current, without built-in overcurrent protection. Designed to protect a person from electric shock in case of accidental unintentional touching live parts of electrical installations and prevents fires due to leakage currents to earth. It does not have its own electricity consumption and has a high mechanical durability. VD 1-63 type AC fully complies with the requirements of GOST 50326 and GOST 50807 as a differential switch "functionally independent of the power source".
• The residual current device VD1-63 is designed for use in power grids to which modern household appliances (TVs, washing machines, computer equipment, etc.) can be connected, as well as for power supply of industrial facilities where electronic equipment is used.

• electromechanical RCD capable of functioning without auxiliary power supplies
• electromechanical circuit without electronic components
• high mechanical durability. At least 10,000 inclusions
• rated conditional differential short-circuit current 4500 A
• silver soldered contacts
• wide range in accordance with the requirements of the standard from 10 to 100 mA
• the most reliable protection of a person in case of direct contact with live parts
• independent contact position indicator
• wide range of operating temperatures from -25 ° С to +50 ° С
• does not have its own power consumption and remains operational in the event of a break in the neutral conductor
• presence of a button TEST

Figure: 2 Three-phase RCD type AC

Figure: 3 Single-phase RCD type AC

• electromechanical circuit without electronic components. Does not have its own electricity consumption and remains operational in the event of a break in the neutral conductor
• wide range of operating temperatures from –25 ° С to +50 ° С allows the use of RCDs in various climatic zones
• oversized screw head with universal slot facilitates installation and prevents screws from falling out during installation
• arcing grilles in each pole. Increased response time due to the use of a special design of the release mechanism
• rated conditional residual short-circuit current 4500 A. Main circuit status indicator provides accurate information on the state of the contacts regardless of the position of the handle
• notches on the terminals reduce heat losses and increase the mechanical stability of the connection
• button TEST to check the functionality of the device and correct connection
• More than 50 standard versions for 10 rated currents.
• Complies with GOST R 51326.1-99 and is manufactured according to TU 3421-033-18461115-02.
• Specifications:

Rated voltage with a frequency of 50 Hz, V
Rated current Iн, А	16, 25, 32, 40, 50, 63, 80, 100
Rated breaking differential current I Dn, mA	10, 30, 100, 300
Rated conditional residual current short circuit I Dс, A
Performance with differential current
Trip time at rated differential current, ms
Number of poles
terms of Use
Breaker protection degree
Electrical durability, cycles B-O, not less
Mechanical durability, cycles B-O, not less
Operating temperature range, ° С
Presence of precious metals (silver), g / pole
Weight (2/4-pole), kg
Maximum cross-section of the connected wires, mm 2

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Unfortunately, our consumers do not always pay due attention to this indicator. Taking advantage of this, unscrupulous merchants supply the Russian market with cheap, often outdated models of devices with low Inc - 3000 A and even 1500 A. The consequence of the use of such low-quality devices is numerous fires and failure of electrical equipment. It should be noted that in European countries, RCDs with I nc less than 6 kA are not allowed to operate. For high-quality RCDs, this indicator is 10 kA and even 15 kA.

On the front panel of the devices, this indicator is indicated either by a symbol: for example, I nc \u003d 10,000 A, or by the corresponding numbers in a rectangle.

The switching capacity of the RCD - I m, according to the requirements of the standards, must be at least ten times the rated current or 500 A (the larger value is taken).

The value of this parameter of a specific device is determined by the design of the tripping mechanism, the quality of the contacts.

High-quality devices, as a rule, have a much higher switching capacity - 1000, 1500 A. This means that such devices are more reliable, and in emergency modes, for example, with a short circuit to earth, the RCD, ahead of the circuit breaker, will be guaranteed to trip.

Currently, three standards are in force - GOST R 50807-95, GOST R 51326.1-99 (RCD without built-in overcurrent protection) and GOST R 51327.1-99 (RCD with built-in overcurrent protection), which determine the parameters of the RCD.

Further, the main parameters of the RCD are considered, the definitions of these parameters are given in accordance with the specified standards, the most important parameters are considered in more detail. RCDs with built-in overcurrent protection have only a few additional features. Hereinafter referred to as "RCD" devices without built-in overcurrent protection, and the terms and definitions relating to RCDs with built-in overcurrent protection will be indicated specifically.

5.2. RATED VOLTAGE U n

The rated voltage of the RCD is the voltage value set by the manufacturer for the given operating conditions, at which its operability is ensured.

It is permissible to use a four-pole RCD in a two-pole mode, i.e. in a single-phase network, provided that the manufacturer ensures the normal functioning of the operational control circuit ("Test" button) at this voltage.

The norms also establish the voltage range in which the RCD must remain operational, which is of fundamental importance for RCDs functionally dependent on the supply voltage.

Functionally independent of the supply voltage (electromechanical) devices remain operational at any voltage values \u200b\u200band even in the absence of voltage, for example, when the neutral conductor is broken.

5.3. RATED INSULATION VOLTAGE U i

The rated insulation voltage U i is the voltage value set by the manufacturer at which the test voltage is determined during the insulation test and the RCD creepage distance.

Unless otherwise specified, the rated insulation voltage is the maximum rated voltage of the RCD. The value of the maximum rated voltage of the RCD must not exceed the value of the rated insulation voltage.

5.4. RATED CURRENT I n

Rated current I n - the current specified by the manufacturer that the RCD can conduct in continuous operation at a set control ambient temperature.

For RCDs with built-in overcurrent protection, the rated current I n is also the rated current of the circuit breaker as part of the RCD, the value of which is used to determine by calculation or according to the tripping time diagrams for overcurrents.

Continuous operation means continuous operation of the device for a long period of time, calculated at least in years.

The standard reference ambient temperature is 30 ° C.

The rated current I n of the RCD is selected from the range: 10, 13, 16, 20, 25, 32, 40, 63, 80, 100, 125 A. For RCDs with built-in overcurrent protection, values \u200b\u200bof 6 and 8 A are additionally entered.

For an RCD, the value of this current is determined, as a rule, by the cross-section of the conductors in the device itself and the design of the power contacts.

Since the RCD must be protected by a serial protective device (ROM), the rated current of the RCD must be coordinated with the rated current of the ROM. No ROM is required for RCDs with built-in overcurrent protection.

In foreign normative documents (for example, in the Austrian CE EN1, T1, §12.12) there is a requirement to increase the RCD rated current by a step relative to the rated current of the series protective device.

This means that, for example, in a circuit protected by a circuit breaker with a rated current of 25 A, determined according to the method described in Ch. 7, an RCD with a rated current of 40 (32) A must be installed (Table 5.1).

Table 5.1

The expediency of such a requirement can be explained by a simple example.

If the RCD and the circuit breaker have equal rated currents, then when an operating current flows that exceeds the rated one, for example, by 45%, i.e. overload current, this current will be disconnected by the circuit breaker for a period of up to one hour. This means that during this time the RCD will be overloaded. Obviously, this drawback is organically inherent in RCDs with built-in overcurrent protection, which have one common (for both RCD and built-in circuit breaker) parameter - rated load current.

5.5. RATED FREQUENCY f n

Rated frequency f n is the industrial frequency for which the RCD is designed and to which the values \u200b\u200bof other characteristics correspond.

There are special RCDs designed for a specific frequency range - for example, 16-60 Hz, 150-400 Hz.

5.6. RATED BREAKING DIFFERENTIAL CURRENT I n

The rated residual tripping current I n is the value of the residual tripping current specified by the manufacturer at which the RCD must trip under the specified conditions. In domestic electrical engineering practice and, in particular, in relay protection, the term "setting" has been used for many years. With regard to RCDs, the rated residual current is the setting.

The rated breaking differential current (setting) of the RCD is selected from the following range: 6, 10, 30, 100, 300, 500 mA.

In practice, the RCD setting for each specific application is selected taking into account the following factors:

• the value of the total (taking into account the connected stationary and portable electric receivers) leakage current to earth existing in the given electrical installation - the so-called "background leakage current";
• values \u200b\u200bof permissible current through a person based on electrical safety criteria;
• the real value of the RCD tripping differential current, which, in accordance with the requirements of GOST R 50807-94, is in the range 0.5 I n - I n.

According to the requirements of the PUE (7th ed., Clause 7.1.83), the rated differential breaking current of the RCD (setting) must be at least three times higher than the total leakage current of the protected circuit of the electrical installation - I .

I n  3 I 

The total leakage current of an electrical installation is measured by special devices (Section 9), or determined by calculation.

In the absence of actual (measured) values \u200b\u200bof the leakage current in the electrical installation PUE (clause 7.1.83), it is prescribed to take the leakage current of electrical receivers at the rate of 0.4 mA per 1 A of the load current, and the leakage current of the circuit at the rate of 10 μA per 1 m of the length of the phase conductor ...

In some cases, for certain consumers, the setpoint value is set by regulatory documents.

Table 5.2

Table 5.3

VDE section	Application	Setting I n,
0100 - 559	Luminaires, lighting installations	 30 mA
0100 - 701	Bathrooms and showers	 30 mA
0100 - 702	Indoor and outdoor pools	 30 mA
0100 - 704	Construction sites
Socket circuits (single-phase) up to 16 A	 30 mA
Other socket chains	 500 mA
0100 - 705	Agricultural electrical installations
common circuits	 500 mA
socket chains	 30 mA
0100 - 706	Rooms with electrically conductive walls and limited movement	 30 mA
0100 - 708	Food points for mobile vans	 30 mA
0100 - 720	Fire hazardous industrial premises	 500 mA
0100 - 721	Mobile RVs, Boats and Yachts, Camping Power Systems	 30 mA
0100 - 722	Flying objects, cars, residential trailers (R z  30 Ohm)	 500 mA
0100 - 723	Training rooms with laboratory stands	 30 mA
0100 - 728	Redundant power systems (R z  100 Ohm)	 500 mA
0100 - 737	Damp and humid rooms Open installations: socket circuits up to 32 A	 30 mA
0100 - 738	Fountains	 30 mA
0100 - 470	Socket circuits in open electrical installations	 30 mA
	Medical premises
at I n  63 A	I n  30 mA
at I n\u003e 63 A	I n  300 mA
0118 - 1	Underground structures	 500 mA
0544 h 100	Electric welding plants, arc welding equipment	 30 mA
0544 - 1	Spot welding machines	free choice
0660 - 501	Switchboards on construction sites	 500 mA
	Traffic control devices, traffic lights (I n  25 A)	 500 mA

In GOST R 50669-94, as applied to buildings made of metal or with a metal frame, the RCD setting value is not higher than 30 mA.

The Temporary Directives prescribe:

• for plumbing cabins, bathrooms and showers, install an RCD with a trigger current of 10 mA, if a separate line is allocated to them;
• in other cases, (for example, when using one line for a plumbing booth, kitchen and corridor), it is allowed to use an RCD with a setting of 30 mA (clause 4.15);
• in individual residential buildings for group circuits supplying sockets inside the house, including basements, built-in and attached garages, as well as in group networks supplying bathrooms, showers and saunas RCDs with a setting of 30 mA;
• for externally installed RCD sockets with a setting of 30 mA (p. 6.5).

The sockets of construction sites must be protected by using an RCD with a tripping current of no more than 30 mA (clause 704.471 GOST R 50571.23-2000).

To protect against fires, the electrical circuit must be protected by an RCD with a rated breaking differential current not exceeding 0.5 A (p. 482.2.10 GOST R 50571.17-2000).

As an example, in table. 5.3 shows the values \u200b\u200bof the leakage current setpoints prescribed by the German VDE electrical code for various objects.

As discussed in section 4.3 of this publication, the AC type RCD responds to alternating sinusoidal differential currents, while the A type responds to alternating sinusoidal differential currents and pulsating DC differential currents.

Since the effective value of the pulsating rectified alternating current differs from the effective value of the alternating current of the same amplitude, the value of the tripping differential current of the RCD type "A" also differs from the similar parameter of the RCD type "AC".

GOST R 51326.1-99 (Table 17) shows the ranges of the tripping current of type "A" RCDs depending on the signal shape (delay angle) of the differential current - Table 5.4.

Table 5.4

RCDs of type "A" are checked for correct operation with a uniform increase in the differential pulsating direct current from zero to the value 2 I n (for RCDs with I n  10 mA) or up to 1.4 I n (for RCDs with I n \u003e 10 mA) in 30 seconds.

Similarly, the RCD of type "A" is checked for correct operation when a smooth direct current of 0.006 A is applied. The superimposed smooth direct current of 6 mA should not affect the value of the tripping differential current.

Thus, the tripping differential current of type "A" RCDs during the flow of pulsating differential currents can have values \u200b\u200bfrom 0.11 I n to 2 I n.

5.7. RATED NON-CUTTING DIFFERENTIAL CURRENT I nо

The rated non-breaking differential current I no is the manufacturer's specified non-breaking differential current at which the RCD will not trip under the specified conditions.

It has already been indicated above that the rated non-breaking sinusoidal differential current of the RCD is equal to half the value of the setting current:

I n0 \u003d 0.5 I nn.

This means that the sinusoidal breaking current is between the rated residual breaking current and the rated non-breaking residual current. If a residual current that is less than the rated non-breaking residual current flows through the RCD, the RCD should not trip.

The value of the sinusoidal differential current, at which the RCD automatically trips, must be in the range from I n0 to I n - the trip range.

For RCDs of type "A" with pulsating constant differential current, the operating range depends on the angle of the current delay (Table 5.4).

It follows from the table that the operating range for RCDs of type "A" with pulsating constant differential current is much wider than with sinusoidal differential current. Its lower limit is 0.11 I n, and the upper limit is higher than the rated residual current breaking and can be 1.4 I n or 2 I n (depending on the RCD IDn).

Thus, for type "A" RCDs, the nominal non-disconnecting sinusoidal differential current is 0.5 I n, and the minimum (at a delay angle of 135 °) non-disconnecting pulsating constant differential current is 0.11 I n.

When designing electrical installations and choosing RCD settings, it is necessary to take into account the existing "background" currents and the specified feature of the RCD type "A".

5.8. RATED OFF TIME T n

Standards GOST R 51326.1-99 and GOST R 51327.1-99 establish two time parameters of the RCD - the trip time and the maximum non-trip time (for RCD type "S").

The RCD trip time is the time interval between the moment of the sudden appearance of the tripping differential current and the moment the arc is extinguished at all poles of the RCD.

The maximum time of non-disconnection (non-operation) for RCDs of type "S" is the maximum time interval from the moment when the residual current tripping in the main circuit of the RCD occurs until the moment when the breaking contacts are pulled out.

The maximum non-tripping time is a time delay that allows to achieve the selectivity of the RCD when working in multi-level protection systems (see section 8.5.).

The time characteristics of the RCD are given in table. 5.5.

Table 5.5

From table. 5.5 it follows that the maximum permissible RCD disconnection time is 0.3 s (0.5 s for an "S" type RCD).

In fact, modern high-quality electromechanical RCDs have a response speed of 20-30 ms.

This means that the RCD is a "fast" switch, therefore, in practice, situations are possible when the RCD trips before the overcurrent protection device and disconnects both load currents and overcurrents.

5.9. LIMITING VALUE OF OVERCURRENT OF NON-CUTTING-OFF I nm

When the overcurrent flows through the main circuit of the RCD, it can be triggered even if there is no differential current in its main circuit - the so-called "false" disconnection of the RCD occurs.

The reason for the erroneous operation of the RCD is the appearance in the secondary winding of the differential current transformer of an unbalance that exceeds the sensitivity threshold of the RCD release.

The GOST R 51326.1-99 standard establishes the limit value of the overcurrent flowing through the main circuit of the RCD, which does not cause its automatic operation, provided that there is no differential current in the main circuit of the RCD.

This value is equal to 6 I n both for the case of a multi-phase uniform load of a multi-pole RCD, and for the case of a single-phase load of a three- and four-pole RCD.

The parameter "limit value of overcurrent of non-disconnection" characterizes the ability of the RCD not to react to symmetrical currents of short circuit and overload (up to a certain value) and is an important indicator of the quality of the device.

The standards define the minimum value of the non-disconnecting current, the maximum value of the non-disconnecting overcurrent is not standardized and can be much higher than 6 I n.

For RCDs with overcurrent protection, this parameter has a different meaning, since the overcurrent is disconnected by the automatic switch built into the RCD. GOST R 51327.1-99 includes requirements for checking the limiting non-operating current in the event of a short circuit. The test procedure provides for checking the limit value of the overcurrent in the case of a single-phase load of a four-pole RCD. For this, in the main circuit of the RCD, a current is set equal to 0.8 of the value of the lower limit of the corresponding characteristics of instantaneous tripping (types B - 2.4 I n, C - 4 I n and D - 8 I n). The RCD should not trip within 1 second.

5.10. RATED ON AND OFF CAPACITY (SWITCHING CAPACITY) I m

The rated making and breaking capacity is one of the most important characteristics of an RCD, which determines its quality and reliability. According to GOST R 51326.1-99, the rated maximum making and breaking capacity is the rms value of the alternating component of the expected current specified by the manufacturer, which the RCD is capable of making, conducting and breaking under specified conditions (if there is a residual current in the main circuit of the RCD).

According to the requirements of the standard, I m must be at least 10 I n or 500 A (the larger value is taken).

The switching capacity depends on the level of technical performance of the device - the quality of the power contacts, the power of the spring drive, the material (plastic or metal parts), the accuracy of the drive mechanism, the presence of an arc suppression chamber, etc. This parameter largely determines the reliability of the RCD.

In some emergency modes, the RCD must disconnect overcurrents, ahead of the circuit breaker, while it must retain its operability.

5.11. RATED MAKING AND MAKING BREAKING CAPACITY FOR DIFFERENTIAL CURRENT I m

According to GOST R 51326.1-99, the rated maximum differential making and breaking capacity I m is the rms value of the alternating component of the expected differential current indicated by the manufacturer, which the RCD is capable of making, conducting and breaking under specified conditions. The minimum value of the rated maximum residual making and breaking capacity I m is 10 I n or 500 A, whichever is greater.

5.12. RATED CONDITIONAL SHORT-CIRCUIT CURRENT I nc

The rated conditional short-circuit current is the most important RCD parameter, which characterizes, first of all, the quality of the product.

The factory-specified value for this parameter is verified during certification testing of the device. The values \u200b\u200bof the rated conditional short-circuit current are standardized and equal: 3000, 4500, 6000 and 10000 A.

The meaning of the test is to determine the thermal and electrodynamic resistance of the product during the flow of overcurrents.

When tested on a special stand, a circuit is created from a powerful source and load, which ensures the flow of a given overcurrent through the RCD for a very short time - until the protective device is triggered (fuse-links in the form of silver conductors of a calibrated section or simply calibrated fuses).

The test current (Figure 5.1) does not reach the specified amplitude value, since it is switched off by a previously connected in series protective device with a normalized setting. However, the steepness of the front of the electrical impulse applied to the RCD and the energy passed through the RCD during such a test are very high. If the device does not deteriorate and remains operational after such a tough test, this means that its quality is at a high level.

The value of I nc, as the most important parameter of the RCD, must be given on the front panel of the device, or in the accompanying technical documentation for the RCD.

For RCDs of types "S" and "G" (with a delayed actuation), increased requirements are imposed on this parameter, since it is assumed that, firstly, RCDs of this type are installed on the head section of the network, where short-circuit currents are naturally higher, during - secondly, such devices, having a response delay, can be under the influence of emergency overcurrents for a longer time.

5.13. RATED CONDITIONAL SHORT-CIRCUIT DIFFERENTIAL CURRENT I s

This parameter and test procedure are similar to those discussed in clause 5.12. The main difference is that when testing an RCD for resistance to a differential short-circuit current, the test overcurrent is passed alternately through the individual poles of the RCD. This means that this test is even tougher than the one described above, since in this case there is no mutual compensation of the magnetic fields of the currents of the primary winding of the transformer.

The values \u200b\u200bof the rated conditional residual short-circuit current I с are standardized and equal: 3000, 4500, 6000 and 10000 A.

This parameter characterizes the resistance of the device to overcurrent flow through one pole.

The RCD with a differential overcurrent will operate with the maximum speed, however, in this case, since the overcurrent is transformed into the secondary winding, the load on the differential current transformer and on the magnetoelectric release is very high.

For RCDs that depend on the supply voltage, the differential overcurrent mode is especially dangerous. For example, there have been cases of failure of the input circuits of electronic amplifiers connected to the secondary winding of a current transformer.

In practice, the differential overcurrent mode occurs, for example, in the TN-C-S system with a dead short circuit behind the RCD of the phase conductor to N- or PE-conductors.

5.14. CHARACTERISTIC I 2 t (Joule integral)

Historically, in the electric power industry, the Joule integral - the integral of the square-law current over a given time interval was used to assess the thermal resistance of cables, buses, connections, electrical devices, etc. in case of short circuits. The integral was determined by calculation by the value of the short-circuit current during its course - from the moment the short-circuit current appeared until the moment the arc was extinguished at the contacts of the power switch. The integral made it possible to determine the amount of energy released at a certain object during the duration of the short circuit.

For RCDs, the standard defines the I 2 t characteristic as a curve giving the maximum I 2 t value as a function of the expected current under the specified operating conditions:

The Joule integral determines the amount of energy passed through the RCD when tested for conditional short-circuit current. This characteristic is energetic, it makes it possible to comprehensively assess the resistance of the device when a certain amount of energy passes through it. When a test current flows through the RCD, part of the energy is released in the RCD structure in the form of heat, dynamic forces applied to the conductors, the insulating elements of the device.

The Joule integral for an RCD with overcurrent protection has a slightly different meaning. It is defined for an integrated overcurrent protection device - a circuit breaker.

The Joule integral as a characteristic of a circuit breaker determines the amount of energy that a circuit breaker can pass through itself until the short-circuit current is cut off.

This indicator has acquired particular importance with the advent of modern circuit breakers with current-limiting properties, achieved with the help of special design solutions - in particular, the design of the arc chute and the magnetic blowing system for arc extinguishing. In the old designs of circuit breakers with natural arc extinction at the moment of the current crossing "zero", the Joule integral was determined by the full half-wave of the sinusoidal current. The Joule integral of circuit breakers with current-limiting properties is much less (Fig. 5.2) - in high-quality circuit breakers, the arc is extinguished in a quarter of the power frequency period.

In terms of current limitation, circuit breakers are divided into three classes - 1, 2, 3. The higher the class of the circuit breaker, the more energy it is able to pass, the less the thermal effect of the short-circuit current in the protected circuit.

Currently, in Germany, the norms for the installation of electrical installations for residential buildings allow for the use of circuit breakers with a rated breaking capacity of at least 6000 A and an energy limitation class of at least 3. Circuit breakers are marked with the appropriate sign - for example,.

The limit values \u200b\u200bof the characteristic I 2 t (transmitted energy in A2c) for circuit breakers according to EN 60898 D.5.2.b for circuit breakers up to 16 A (type B) and from 20 A to 32 A (type B) are given in table 5.6.

Table 5.6

Rated breaking capacity, A	Energy limiting class
I n  16 A
3 000	Not standardized	31 000	15 000
6 000	100 000	35 000
10 000	240 000	70 000
20 A< I n  32 А
3 000	Not standardized	40 000	18 000
6 000	130 000	45 000
10 000	310 000	90 000

Examples of characteristics I 2 t of circuit breakers and RCDs are shown in Fig. 5.3-5.4.

For circuit breakers that are part of an RCD with built-in overcurrent protection, the GOST R 51327.1-99 standard establishes a time-current characteristic zone, similar to the requirements for circuit breakers in GOST R 50345-99 “Small-sized electrical equipment. Circuit breakers for overcurrent protection for household and similar purposes. " The zone of the time-current trip characteristic of an RCD with built-in overcurrent protection is determined by the conditions and values \u200b\u200bspecified in Table 5.7.

Table 5.7

Test	A type	Test current	Initial state	Tripping or non-tripping time	Desired result	Note
a	B, C, D	1.13 I n	Cold	t  1 h (for I n< 63 А) t  2 ч (при I n > 63A)	Without decoupling	-
b	B, C, D	1.45 I n	Immediately after the test a	t< 1 ч (при I n < 63 А) t < 2 ч (при I n > 63A)	Decoupling	Continuous rise of current for 5 s
c	B, C, D	2.55 I n	Cold	1 sec< t < 60 c (при I n < 32А) 1 с < t < 120 c(при I n > 32A)	Decoupling	-
d	B	3 I n	Cold	t\u003e 0.1 s	Without decoupling
C	5 I n
D	10 I n
e	B	5 I n	Cold	t< 0,1 с	Decoupling	The current is generated by closing the auxiliary switch
C	10 I n
D	50 I n

5.15. RATED GREATER SWITCHING CAPACITY I cn

For RCDs with built-in overcurrent protection GOST R 51327.1-99 defines this parameter as follows: "The rated maximum switching capacity I cn is the value of the maximum breaking capacity specified by the manufacturer."

Ultimate short-circuit breaking capacity is the breaking capacity for which the prescribed conditions according to the specified test cycle do not provide for the ability of the RCD to carry, for a specified time, a current equal to 0.85 non-breaking current.

The considered characteristic in GOST R 50345-92 is called "rated breaking capacity".

According to GOST R 51327.1-99, the standard values \u200b\u200bof the maximum rated switching capacity up to 10,000 A inclusive are equal to 1500, 3000, 4500, 6000, 10000 A.

The standard specifies that during testing, each RCD with overcurrent protection must provide one trip of the test electric circuit with an expected overcurrent equal to the rated maximum switching capacity, as well as one turn-on followed by automatic shutdown of the electric circuit in which the specified test current flows.

After these tests, the RCD should not have any damage that would impair its operational properties, and should also withstand the dielectric strength tests and tripping characteristics established by the standard.

5.16. OPERATING GREATEST BREAKING CAPACITY I cs

The operating short-circuit breaking capacity of an RCD with overcurrent protection is the breaking capacity for which the prescribed conditions, according to the specified test cycle, provide for the ability to carry, for a specified time, a current equal to 0.85 of the non-tripping current.

The relationship between the working I cs and the rated Icn with the highest switching capacities (according to table 18 of GOST R 51327.1-99) is as follows.

For I cn \u003d 6000 A, the working I cs and nominal I cn are equal to I cs \u003d I cn, for the range of I cn values \u200b\u200bfrom 6000 A to 10000 A I cs \u003d 0.75 I cn, but not less than 6000 A, for I cn\u003e 10000 A I cs \u003d 0.5 I cn, but not less than 7500 A.

6. OPERATIONAL CHARACTERISTICS OF RCD
6.1. NORMAL CONDITIONS OF USE

Due to its special purpose - protection of human life and property - the RCD has extremely high requirements for reliability, noise immunity, thermal and electrodynamic resistance, materials and design. These special requirements partly explain the relatively high cost of modern high-quality RCDs that meet the requirements of standards and have appropriate certificates.

The standards GOST R 51326.1-99 and GOST R 51327.1-99 define the following normal operating conditions for an RCD:

• ambient air temperature from -5 ° С to + 40 ° С, average daily value no more than + 35 ° С (storage of products is allowed at ambient temperatures from -20 ° С to + 60 ° С);
• the height of the installation site above sea level should not exceed 2000 m;
• relative air humidity not more than 50% at an ambient temperature of + 40 ° С (an increase is possible at lower ambient temperatures, for example, up to 90% at + 20 ° С);
• external magnetic fields should not exceed five times the value of the Earth's magnetic field in any direction;
• frequency - nominal frequency value ± 5%;
• distortion of the sinusoidal shape of the curve - no more than 5%.

6.2. EXCEEDING TEMPERATURE

During operation, when the operating load current flows through the RCD, the current-carrying elements and the device structure are heated.

The GOST R 51326.1-99 standard defines the limits for the temperature rise of the RCD parts (relative to the ambient temperature) when the current flows through its main circuit equal to the nominal one.

Table 6.1 shows the temperature rise values \u200b\u200bdefined by the standards.

Table 6.1

6.3. DEGREE OF PROTECTION

According to GOST R 14254-96 "Degrees of protection provided by enclosures (IP Code)", the degree of protection of an RCD under normal operating conditions - after completion of installation, must correspond to class IР20.

According to GOST R 51327.1-99, RCDs must be designed in such a way that after installation and connection, as for normal operation, their live parts are inaccessible to touch.

Some companies produce RCDs of a higher protection class - for example, IР25, IР40.

When installing an RCD in special climatic conditions, it is placed in a protective casing.

6.4. DISCONNECTING FUNCTION

According to GOST R 51327.1-99, an RCD has a mechanical switching device designed to turn on, conduct and turn off currents under normal operating conditions, as well as disconnect contacts when the differential current reaches a specified value under certain conditions.

According to GOST R 50030.1-92, the disconnection function is an action aimed at turning off the power supply of the entire installation or its separate part by separating this installation or part of it from any source of electrical energy for safety reasons.

The design of the RCD provides a disconnect function.

Air gaps and creepage distances of RCDs must meet the requirements of standards - GOST R 51326.1-99 (Table 3), GOST R51327.1-99 (Table 5). The circuit breakers also perform the disconnecting function - GOST R 50345-99 (Table 3).

Permissible air gaps and creepage distances of the RCD are given in table. 6.2.

The RCD must have a free trip mechanism necessary so that the moving contacts can be at rest only in the closed or open position, even when the controls are in any intermediate position.

Moving contacts of all poles of a four-pole RCD must be mechanically connected in such a way that all poles, except for the commutating zero working one, turn on and off almost simultaneously, regardless of how the operation is carried out - manually or automatically.

The contacts of the pole that commutes the neutral working conductor must close earlier and disconnect later than the contacts of the other poles (T \u003d 3-4 ms).

Table 6.2

Name	Value, mm, not less
Air gaps:
1) between live parts disconnected when the RCD is open
3) between live parts and:
- the surface on which the base is mounted
- screws and other means of fastening the covers, which must be removed during the installation of the RCD
- other accessible metal parts
Creepage distances:
1) between live parts disconnected when the RCD is closed
2) between live parts of different polarity
3) between live parts and:
- screws and other means of fastening the covers, which must be removed during installation
- available metal parts

6.5. ELECTRICAL INSULATION PROPERTIES

GOST R 51326.1-99 makes rather high requirements for RCDs in terms of electrical insulation.

According to clause 9.7 of the specified GOST, after the RCD is in a humid chamber with a relative air humidity of 91-95% for 48 hours, the insulation resistance of its main circuit must be at least 2 MΩ, the insulation resistance between the metal parts of the mechanism and the case is at least 5 mΩ. Insulation resistance is measured at 500 VDC.

The dielectric strength of the RCD is tested by applying a test voltage of 2000 V AC 50 Hz to its main circuit for one minute. No overlaps and breakdowns are allowed during the test.

The insulation of the RCD must also withstand the surge test. The tests involve the application of ten current pulses (1.2 / 50 µs) with a peak voltage of 6 kV between the phase poles connected together and the neutral pole. The second set of tests is carried out at a peak pulse voltage of 8 kV. The impulses are applied between the metal base connected to the terminal for the protective conductor (if any) and the phase pole and the neutral pole of the RCD connected together. It is generally accepted that the device has passed the test unless an unintentional destructive discharge has occurred.

6.6. SWITCHING AND MECHANICAL WEAR RESISTANCE

According to the requirements of the standards, switching devices must be able to perform a specified number of mechanical and electrical operating cycles - transfers of moving contacts from an open position to a closed position and vice versa.

The switching durability of any electrical switching device largely depends on the material and design of the contact group. In European countries, electrical standards regulate the materials allowed for use in the manufacture of various types of electrical devices.

For the manufacture of contacts for devices for a specific purpose, various silver alloys are used, characterized by special properties. For example, silver-graphite alloys have the properties of reducing the weldability of contacts at high starting currents, which is important for magnetic starters, silver-tin dioxide alloys provide a low contact resistance of a contact pair at a stable high current load, etc.

For a contact pair (movable - fixed contacts) of the RCD, it is required to use a silver-graphite (AgC) alloy paired with a silver-tungsten (AgW), silver-nickel (AgNi) or silver-tin dioxide (AgSnO 2). The circuit breakers use steam (AgC) and copper (Cu).

In connection with the above, the information given in the advertising brochures of some companies, in which, as an advantage, it is indicated that "silver-plated contacts" are used, is surprising.

Mechanical durability of an RCD is the ability of a device to perform a given number of operations without an electric current flowing through the main circuit.

Switching endurance RCD is the ability of the device to perform a given number of operations while flowing through the main circuit of the rated current at rated voltage.

According to the standards, the RCD during testing must withstand at least:

• 2000 cycles of electrical operation at rated voltage and rated current load;
• 2000 no-load mechanical operating cycles.

The opening operations must be carried out in the following order: for the first thousand cycles using manual means; for the next five hundred cycles using the in-service monitor, the Test button; for the last five hundred cycles by passing one pole of the residual current trip.

After testing, the RCD should not have excessive wear, damage to the shell, allowing the penetration of the standard test finger to the live parts, loosening the electrical and mechanical connections. The standard requires that after this RCD test, a dielectric strength test is carried out without wet pre-treatment.

6.7. CONTROL DEVICE

The design of the RCD without fail provides for the presence of a control device - an operational control device launched by the "Test" button. The purpose of the control device is to periodically monitor the performance of the RCD as a whole.

The control device is a circuit of a test resistor of a certain rating, a closing contact controlled by the "Test" button, and an auxiliary contact mechanically interlocked with a group of RCD power contacts. The auxiliary contact provides disconnection for electrical safety of the test circuit from the power circuit in the disconnected position of the RCD.

When the "Test" button is pressed, a control current of the set value flows through the test circuit, which is differential tripping for the RCD, which should cause the RCD to trip.

The differential breaking current generated by the control device, according to GOST R 51326.1-99, GOST R 51327.1-99, must not exceed 2.5 times the rated breaking differential current of the RCD.

The control device must function reliably with a voltage deviation in the range from 0.85 to 1.1 from the nominal value.

6.8. RCD CONNECTION DIAGRAMS

The designs of RCDs from different manufacturers may differ from each other not only in parameters, but also in the connection diagrams of the control device.

In fig. 6.1 shows various schemes for switching on the RCD, taking into account the internal scheme of connecting the control device to the external terminals. Also shown is the correct switching on of the RCD in one-, two- and three-phase versions.

Figure: 6.1. RCD connection diagrams
a, b - two-pole RCDs; c, d, e, h - four-pole RCDs (test resistor is connected to phase voltage); f, g, u, k - four-pole RCD (test resistor is connected to line voltage)

In open-phase versions, it is necessary to connect the RCD in such a way that the control device circuit is provided.

The internal connection diagram of the test resistor must be shown on the front or side surface of the RCD case.

6.9. IMPULSE VOLTAGE RCD RESISTANCE

RCDs must be resistant to possible switching and atmospheric overvoltage impulses occurring in electrical installations. Checking the RCD resistance to unwanted operation from voltage pulses for RCDs is carried out using a “ringing wave” pulse generator (GOST R 51326.1-99, GOST R 51327.1-99).

Compliance is checked as follows. 10 current pulses are applied to one of the RCD poles with a peak current value of 200 A, the polarity of the wave must change after every two pulses. The interval between two successive pulses (0.5 μs / 100 kHz) 200 A should be 30 seconds. Type “S” RCDs are tested with a pulse current of 8/20 µs with a peak value of 3000 A. The RCD shall not trip during the test.

6.10. FIRE SAFETY REQUIREMENTS

The design of the RCD should ensure its fire safety and operability both in normal operation and in the event of possible malfunctions and violation of operating rules.

The norms of the state fire service of the Ministry of Internal Affairs of Russia - NPB-243-97 “Fire safety standards. Residual current devices. Safety requirements. Test Methods "establish requirements for RCDs in the design, installation and certification in order to ensure fire safety of electrical installations of newly constructed and reconstructed residential and public buildings, regardless of the form of ownership and departmental affiliation.

According to NPB-243-97, the functional characteristics of the RCD must comply with the requirements set out in GOST R 50807-95.

NPB-243-97 (clause 4.2) impose the following requirements on electrical insulating and structural plastic materials used for the manufacture of RCDs.

The materials from which the outer parts of the RCD are made (except for decorative elements), as well as those used in the design of electrical connections to support live parts in a certain position, must withstand the ball pressure test.

The materials from which the RCD parts are made must be resistant to the effects of the burner flame.

Insulating materials supporting the structures of screw contact joints must be resistant to thermal energy released in the contact resistance of a defective contact joint, as well as resistant to heated wire (960 ° C).

Materials through which a conductive bridge can form between parts of different polarity and different potential must be tracking resistant.

The design of the RCD should exclude the appearance during operation and testing for fire hazard of flame, smoke, softening and melting of structural materials.

NPB-243-97 clause 4.3 states:

“The design of the RCD should ensure its fire safety and operability both in normal operation and in the event of possible malfunctions and violations of operating rules. In this case, the probability of a fire in (from) the RCD should not exceed 10-6 per year. "

By order of the GUGPS of the Ministry of Internal Affairs of Russia No. 73 dated November 17, 98, UZO are included in the list of products subject to mandatory certification in the field of fire safety according to NPB 243-97 and must pass certification tests at the All-Russian Research Institute of Fire Defense of the Ministry of Internal Affairs of Russia (VNIIPO).

If you paid attention to this article, you probably not so long ago asked the question - "What is an RCD and what is its purpose?" We will try to answer this question in as much detail as possible. Well, for starters, let's say that the abbreviation RCD stands for residual current device.

What is an RCD in electrical

Despite the fact that nowadays electrical wiring is maximally protected from contact with people and the sad consequences, there is no escape from leaks. It is then that the RCD will become an indispensable assistant. The device will react with lightning speed to an increased current value at the point of leakage and cut off the power supply.

RCD - this is one of the main "screws" in the protective automation of current electrical networks. The device switches electrical circuits and protects them from currents that flow along undesirable conductive paths under standard conditions. This will increase the chances that your home or business will be protected from fires and no one will be harmed by the electric shock.

Note that this device has a function to turn on or off electrical circuits. In other words, it can switch them. Accordingly, the device is switching.

Why install an RCD

Many consumers have heard about the existence of such a miracle device as an RCD, but not everyone knows what it is for. It is possible to understand the general principles of the unit's functioning even without deep knowledge of electricity. Until recently, RCDs were not used in residential buildings. But nowadays everything has changed, and now devices are increasingly found in apartments, so it's worth learning more about them.

As already mentioned, RCDs are installed in order to prevent current leaks, leading to ignition of wiring and fires. In addition, the RCD will protect you from electric shock, which can lead to significant health problems or, God forbid, death if you come into contact with bare wires and conductive sections of electrical equipment.

NOTE! RCDs differ from machines that protect wiring from overloads and short circuits, its purpose is to significantly increase the protection of people.

The principle of operation of the RCD

The operation of the device is based on fixing the leakage current to the "ground" and disconnecting the power grid in the event of such an emergency. The device detects the presence of a leak only by the difference between the currents: those that came out of the device and those that came back.

If everything is in order with the power grid, then the currents are identical in magnitude, but differ in direction. As soon as a leak appears - for example, you touch a 100% uninsulated wire - some of the current goes "to the ground" along another circuit ( in this case - through the human body). As a result, the current returned to the RCD through the neutral will be less than that released.

The same happens if the insulation is damaged in one of the electrical devices. Then the case or other part is energized. By touching them, the person creates another contour “to the ground”. In this case, part of the current will move along it, that is, the balance will be destroyed.

Of course, if the insulation is damaged, then the branch circuit can appear without the participation of the human body. In this situation, the device will also respond 100% and save the network section from the sad consequences such as overheating and fire.

When is it necessary to install an RCD?

The device is indicated for installation where there is a need to protect group lines providing power to plug-in sockets for portable electrical appliances. It is imperative to install an RCD if the circuit breaker or fuse does not provide an auto shutdown time of 0.4 seconds, taking into account the rated voltage of 220 V due to low currents.

In addition, it is recommended to install an RCD if there are people in your family who "love" carelessly handling electrical wiring. The simplest case: a person drills a wall, while resting his bare foot on the battery, and touches the phase wire. It flies along the chain "metal drill body - hand - chest - leg - battery" and leads to dire consequences: heart paralysis or respiratory arrest (sometimes all together). If you have an RCD installed, it will instantly "understand" that some of the current has not returned, and will immediately turn off the electricity. Yes, an electric shock will occur, but the discharge will be minimal.

When will an RCD not help?

RCD does not save from overvoltage, incl. from impulse, as well as from low voltage, which "kills" electric motors - in the refrigerator, washing machine, and so on.

The unit also does not protect against short circuits. This task is performed by the circuit breaker or.

How many RCDs do I need to install?

To determine the exact number of RCDs required for a particular room, you will need a specialist who can carry out the appropriate calculations. For example, in a 1-room apartment, one such device, designed for a leakage current of 30 mA, is most likely enough. But in an apartment with four rooms with 15 groups of outlets, at least five RCDs will be needed, as well as one device for the entire lighting group, an electric stove and a water heater.

It is usually assumed that one group of electrical appliances is one residual current device of 30 mA plus one fire-fighting RCD of 100 or 300 mA.

NOTE! To control the wiring as a whole, it is recommended to install one common RCD at the entrance to a private house with a rated breaking current of 300 mA in addition to the calculated one.

When is the installation of an RCD impractical?

Sometimes it just doesn't make sense to install a device. One of these situations is the presence of old and decrepit wiring. The ability of an RCD to detect a leak can become a headache if the device starts to operate unpredictably ( and this is what happens with poor wiring). In this case, the best solution would be to put the RCD not in the power supply circuit of the apartment as a whole, but in places with increased danger for using outlets.

It also makes no sense to buy a low-quality RCD. In the modern market, you can find not only original devices, but also a wide range of fakes of unknown origin. Many of these devices are made on the knee around the corner. The use of such devices is completely unacceptable and impractical. Before purchasing, carefully study the technical documentation and quality certificates of the purchased unit.

It makes no sense to install the device in lines that give voltage to stationary equipment and lamps, as well as in general power grids.

Device

The RCD device assumes the presence of:

• leakage sensor;
• polarized magnetic relay.

The operation of the device is based on laws based on incoming and outgoing electricity in closed circuits with extremely high loads. This indicates that the current should have only one value, regardless of the phase of passage.

There are three magnetic coils inside the device. The phase passes through the first, through the second zero. The current creates magnetic fields at the input and output of the coils of the device.

If everything works as it should, the mutual fields destroy each other. If an imbalance occurs on one of the coils, that is, a current leak is formed, this will lead to the action of the third coil, which has a relay to turn off the power.

Main technical characteristics

Each RCD has a certain set of technical parameters that should be studied before purchasing:

• manufacturer;
• model name;
• operating current - the limiting value of the current that the device can switch;
• power grid parameters ( voltage and frequency);
• leakage current - the maximum amount of leakage current to which the device reacts;
• type of RCD;
• working temperature range;
• rated conditional short-circuit current;
• rCD device diagram.

Decoding of marking

The marking is applied to the RCD body, which makes the choice of the desired model more convenient and easy. First of all, the manufacturer is indicated, but there is also other important information:

• "RCD" or "VD" - means that this is a residual current device;
• 16A - maximum current for which the product contacts and other internal elements are designed;
• In 30mA - leakage current at which the RCD will trip;
• 230V and 50Hz - voltage and frequency at which the unit operates;
• S - selective RCD;
• “~” sign - it means that the device operates on AC leakage.

In addition, there are labels next to each contact for correct:

• N ( from above) - an incoming neutral conductor is connected to this contact;
• 1(from above) - the incoming phase conductor is connected here;
• 2 (from below) - a phase conductor connected to the load is connected to this place;
• N ( from below) or no letter - the neutral conductor is connected to the load.

In order for the one that is ideal for your power grid, you need to understand the marking in detail, even if this task is very painstaking and tedious.

Types and types

Modern manufacturers offer a variety of types and types of RCDs. The two most popular types of units in terms of their internal design in the electrical goods market are electromechanical ( do not depend on current strength) and electronic ( depend). Selective and fire-fighting devices are also distinguished.

Electromechanical

Electromechanical RCDs are widely used in alternating current electrical circuits. What caused this? The fact that when a leak is detected, such a device will work, preventing the sad consequences even with the smallest voltage.

This type of RCD in many countries is considered a quality standard and one that is mandatory for widespread use. No wonder, because such an RCD will be operational even in the absence of zero in the network and can save someone's life.

Electronic

Such RCDs are easy to find in any construction market. Their difference from electromechanical ones is available inside the board with an amplifier, for which power is required.

However, such RCDs, as already mentioned, have a huge drawback - it is not a fact that they will work with a current leak ( it all depends on the voltage in the network). If zero burns out, and the phase remains, then the risk of electric shock does not disappear.

NOTE! We are talking about the advantages and disadvantages of RCDs in general, and not specific models. If you are very "lucky", you can become the owner of a low-quality RCD, both electromechanical and electronic.

Selective

The main difference between a selective RCD and its "brothers" is the presence in the circuit of the function of the time delay for disconnecting the circuit that powers the load, ie. ... Often this parameter does not exceed 40 ms. From this we conclude that selective devices are not suitable for protection against injury by direct contact.

Another feature of selective aggregates is good stability in the reaction to ( the probability of false positives is almost zero).

Fireproof

As the name suggests, such RCDs are used in the power supply systems of apartments and houses to prevent fires. However, they are not able to protect a person, since the leakage current for which they are designed is 100 or 300 mA.

Usually, these units are installed in metering boards or in floor distribution boards. Their main task:

• protection of the lead-in cable;
• protection of consumer lines in which differential protection is not installed;
• as an additional stage of protection ( if the device below it suddenly did not work).

Number of poles

Since the RCD works by comparing the currents that penetrate through the differential organ, the number of poles in the unit coincides with the number of current-carrying conductors. In some cases, an RCD is allowed to be used with 4 poles for operation in a two- or three-wire network.

In this case, do not forget to leave free phase poles in stock. The unit will successfully do its job not completely, but partially, which, in general, is unprofitable from a financial point of view, but possible.

Conclusion

Every day more and more household electrical appliances appear in our life. Accordingly, the risk of current leakage increases, which sometimes even leads to death. If you are not killed by an electric shock, it will cause serious health problems or provoke a fire. There is one salvation from all these troubles - a residual current device. We strongly advise you to install it at home, as they say, away from sin.

In this article, we'll talk about an electrical device called a fully RCD - residual current device. Residual current device (abbreviated RCD) is a more complete name: residual current device controlled by a differential (residual) current or a mechanical switching device, which, when the differential (residual) current reaches (exceeds) the set value, should cause the contacts to open.

The main task of the RCD (Safety Disconnect Device)

The main purpose of the RCD is to protect a person from electric shock and from a fire caused by current leakage through worn-out wire insulation and poor-quality connections.

Combined devices that combine an RCD and an overcurrent (short circuit) protection device are also widely used. Such devices are called UZO-D with built-in overcurrent (short circuit) protection, or simply diffautomat. Often, diffautomatic devices are equipped with a special indication that allows you to determine the reason for the operation (from overcurrent or from differential current).

Residual current device: purpose

RCD - a residual current device is installed in the electrical network of an apartment or house to perform the following electrical safety tasks:

1. Increasing the level of safety when people use household and similar electrical appliances;
2. Prevention of fires due to ignition of insulation of current-carrying parts of electrical appliances from the differential (residual) current to the ground;
3. For diffautomatics. Automatic shutdown of a section of the electrical network (including apartment) in case of overload (TZ-current protection) and short-circuit current (MTZ-maximum current protection).

Note: In Russia, the use of RCDs became mandatory with the adoption of the 7th edition of the Rules for Electrical Installations (). (The 7th edition was prepared by JSC VNIIE. Approved by order of the Ministry of Energy of the Russian Federation dated 08.07.02 No. 204. Entered into force on 01.01.03.)

Typically, one or more RCDs are installed on a DIN rail in an electrical panel.

(I talked about installing an electrical panel in an apartment in another blog article :)

LET'S SUMMER THE FIRST BRIEF SUMMARY

There are two types of RCDs on sale - Residual current device:

1. Directly RCD.
2. And RCD-D (differential) is RCD + short circuit protection circuit breaker, in "one package".

Important!

• The use of an RCD is an additional protective measure, and not a replacement for overcurrent protection with fuses, since the RCD does not react in any way to malfunctions if they are not accompanied by a current leak (for example, a short circuit between the phase and neutral conductors. Therefore, RCDs must be used in conjunction with Circuit Breakers (fuses)
• An RCD can significantly improve the safety of electrical installations, but it cannot completely eliminate the risk of electric shock or fire. The RCD does not react to emergency situations if they are not accompanied by a leak from the protected circuit. In particular, the RCD does not react to short circuits between phases and neutral.
• The RCD will also not work if a person is energized, but there is no leakage, for example, when a finger touches both the phase and neutral conductors at the same time. It is impossible to provide electrical protection against such touches, since it is impossible to distinguish the flow of current through the human body from the normal flow of current in the load. In such cases, only mechanical protective measures (insulation, non-conductive covers, etc.) are effective, as well as disconnecting the electrical installation before servicing it!

RCD characteristics

Now let's figure out the characteristics of the RCDs indicated on the device case.

UZO - a residual current device designed to protect a person from electric shock when indirectly touching (touching a person to open conductive non-current-carrying parts of an electrical installation that is energized in case of insulation damage), as well as when touching directly (touching a person to live parts of an electrical installation under voltage). This function is provided by an RCD of appropriate sensitivity (cut-off current no more than 30 mA (milliamperes).

Note: In the USA, according to the National Elektrical Code, ground fault circuit interrupter (GFCI) devices designed to protect people must open the circuit at a leakage current of 4-6 mA (milliamperes) (the exact value is chosen by the device manufacturer and is usually 5 mA ) in a time of no more than 25 ms (microseconds). In Europe, these values \u200b\u200bfor RCDs, as in our country, are 30-100 mA.

RCDs should be triggered in a time of no more than 25-40 ms (milliseconds), that is, before the electric current passing through the human body causes cardiac fibrillation - the most common cause of death from electric shock.

The list below shows the values \u200b\u200bof the current through the human body and the most likely sensations that can be felt.

Important! don't try to feel it yourself!

• Current through the human body -0.5mA: not felt, faint sensation when touched with tongue, fingertips and through the wound.
• Current through the human body-3 mA: Feeling close to an ant bite.
• Current through the human body -15mA: If you take hold of the conductor, it is impossible to let it go. It is unpleasant, but safe.
• Current through the human body - 40mA: Body cramps, diaphragm cramps. Danger of suffocation within a few minutes.
• Current through the human body - 80 mA: Vibration of the heart ventricle. Very dangerous, leads to a fairly quick death.

Hence the second short summary of the characteristics of the RCD

To protect a person in household power grids (single-phase current with a voltage of 220 volts), RCDs must be marked: cut-off current no more than 30mA, response time no more than 40 ms (milliseconds). Large manufacturing firms (such as ABB, Legrand) produce RCDs for human protection, with cut-off currents of 10 mA and 30 mA.

An RCD with a current of 30 mA is usually installed on group circuits. If you put an RCD of 10 mA, it is possible (there is always a background, natural leakage current in the apartment). 10 mA is usually put on single consumers (washing machine, dishwasher). If you have a shower, or a washing machine is installed in a bathroom (humid environment), using an RCD with a cut-off current of 10 mA is simple certainly.

It should be repeated:

• For damp and very humid rooms (saunas, baths, bathrooms, showers), an RCD with a leakage current of 10 mA (milliamperes) should be used
• For other premises, it is sufficient to use an RCD with a cut-off current of 30 mA (milliamperes)
• In wooden ladies, when conducting electrical wiring in order to avoid fires, the installation of an RCD is desirable, or rather simply necessary.

Note: On sale there are RCDs with cut-off currents and 100 mA and 300 mA or more. These RCDs (with a breaking differential current of 100 mA, 300 mA or more are sometimes used to protect large sections of electrical networks (for example, in a private house or computer centers), where a low threshold would lead to false alarms. Such low-sensitivity RCDs perform a fire function and do not are effective protection against electric shock.

RCD classification

Now let's note a number of other points. In accordance with the classification, RCDs - residual current devices are subdivided into the following types:

Type AC-RCD, which is guaranteed to trip if the differential sinusoidal current either suddenly appears or slowly increases.

Type A is an RCD, the opening of which is guaranteed in the event that a sinusoidal or pulsating differential current either suddenly appears or slowly increases.

The third result of the article

Type "A" RCDs are more expensive and more versatile, but both Type "A" and "AC" are excellent for use in domestic electrical networks. Therefore, it is not worth emphasizing on this.

In general sale, there are mainly RCDs of the AC type (only the icon will be displayed on the facade of the device:

It should be noted that each RCD is designed for use in networks of a certain load, namely a certain Amperage, which is indicated on the facade of the RCD. Since RCDs in power grids are used together with circuit breakers (fuses), I draw your attention again: the RCD amperage must be higher than that of the machine on the line.

RCD connection diagram

Now we will consider the RCD connection diagram - a residual current device, classic zeroing (TN-C). Most houses in the Russian Federation have classic grounding, there is no separate dedicated grounding line in the apartments of these houses, that is, two rather than three power supply wires run throughout the apartment.

Note: In accordance with GOST 50571_3-94 (Safety requirements. Protection against electric shock):

1. In the TN-C system, protection devices that react to the residual current of the RCD-D should not be used;
2. When an RCD-D differential current protective device is used for automatic tripping in a TN-S system, the PEN conductor must not be used on the load side. The connection of the protective conductor to the PEN conductor (independent earth conductor) must be carried out on the side of the power supply i.e. to a protection device that reacts to differential current (RCD-D). The diagram shows the connection points of the RCD-D.

Before connecting the RCD, I pay attention to how the RCD circuit works. The principle of operation of the RCD is based on a comparison of the current released (left to the apartment) and the current supplied (returned from the apartment). If it turns out that the balance is disturbed, and less comes than it leaves, then the RCD cuts off the power supply. If the RCD is installed for one line, then there are two options: put an automatic device after the RCD, or the device itself must have a built-in maximum current limiter. Connecting an RCD without a machine will lead to the fact that a short circuit or constant overheating can disable it. I remind you that the amperage of the RCD must be higher than that of the machine on the line.

RCD connection diagram

A simple RCD connection diagram is as follows

Note: In the figure, the phase wire is fed to the lower terminal of the input machine. This is not entirely correct, it is better to supply power to the upper terminal of the machine. Although I will note that connecting the power wires from above is just a tradition. It is she, and not some technical reason, that the recommendation for connecting from above is due. And, although from a safety point of view, it would be better to connect everywhere in the same way, there is no strict prohibition on connecting from below. However, it is highly desirable that within the shield, and even better - throughout the facility, power is supplied in the same way: either from above (everywhere) or from below (everywhere). Other connection schemes can be found in the article:.

Well, that's probably all that I wanted to tell you about the RCD - the Protective Disconnect Device used in household electrical networks with a voltage of 220 volts. I wish you success in your endeavors!

Especially for the site: